1. Field of the Invention
The present invention relates generally to a method and apparatus for measuring phase difference between electrical wave forms of a polyphase alternating current signal for use with A. C. Motors or the like, and more particularly, to a phase reversal detection and correction circuit which would operate over a wide range of line frequencies and voltages to insure proper rotation of the motors or the like.
2. Description of the Prior Art
Prior art phase detectors employ bi-stable multi-vibrators or diode configurations with a plurality of transformers to measure the presence or absence of proper phase between incoming sine wave cycles and the required phase sequence of a driven polyphase device. Typically, such circuits operate at a single voltage and are unable to be detect when the incoming three phase power is out of phase if the frequency is not at a single setpoint.